ABSTRACT
Mesocosms (ca. 2 m3) were filled either with clear or humic lake water and biologically treated bleached kraft pulp mill effluent (BKME). One series of the mesocosms was run for one year from June to March and the other from November to December. The formed sediment was collected from the bottom of the enclosures after 275 or 290 d of incubation. Sediments formed in the mesocosms containing both BKME and lake water were different from those formed in the presence of lake water alone. The molar ratio of carbon to chlorine was lower (300) in the BKME-driven sediment compared to reference sediment (2000 to 4000). The halogen content of the sediment formed de novo was dependent on the timing of the start of the experiment. On the average, more sediment-bound halogen per cubic meter of BKME (560 mg Cl) resulted from experiments initiated in the winter than from the summer (140 mg Cl). Sediments in the BKME mesocosms contained tetrahydrofuran-soluble halogens of larger molecular size (1400 g mol−1) than water phase (360 g mol−1) of the same mesocosm after about one year of incubation starting from November. The data indicate that binding of halogen to de novo formed sediment was driven by metabolic activity of the biomass rather than by physical precipitation.
